430 PELONAIA, A NEW GENUS OV TUNIC ATED MOLLUSKS. 



In the mud-filled cavities of old shells from deep water — 

 Anstruther. It has also been taken by Dr. Johnston at Ber- 

 wick. 



Species 2. P. glabra. Test, greenish-yellow, smooth, pilose, 

 not nearly so much elongated as the last. 



Dredged in seven fathoms water, in mud, Rothesay Bay. 



Anatomy of P. glabra. 



1. Muscular System. — The mantle is similar to those of the 

 other Ascidiw, possessing longitudinal and circular fibres. A 

 strong band of transverse fibres passes round the mantle, im- 

 mediately below the anal orifice, encroaching on the cavity 

 principally on that side. The chief peculiarity of the mantle 

 is its firm adhesion to the test. 



2. Digestive and Respiratory Systems. — The respiratory 

 opening is of small size, and exhibits no folds or tentacular 

 fringes. The respiratory sac is elongated, cylindrical, con- 

 tracting rather suddenly towards one side to become continu- 

 ous with the oesophagus. On the external surface of the sac 

 there are about thirty parallel transverse ridges, which give 

 it the appearance of a plaited frill. These plaits are less 

 apparent along the course of the branchial artery and branchial 

 vein, but midway between them on each side they are very 

 prominent, and are tied each by a minute cord to the inner 

 surface of the mantle. The internal surface of the sac exhibits 

 along one side the serpentine double cord which contains the 

 branchial vein ; along the other side the branchial artery ; 

 and from these primary and secondary perpendicular branches 

 proceeding, as in the other Ascidiw. The transverse plaits 

 on the external surface of the sac correspond to the primary 

 or transverse branches of the vessels on the internal surface. 

 The animal was not examined when alive, but cilia without 

 doubt exist in great abundance on the edges of the lozenge- 

 shaped spaces of the sac. 



